The present invention relates to a blow-molded plastic container and a corresponding closure produced by a combination of blow molding/compression molding techniques, and more particularly, the present invention relates to a method and apparatus for the simultaneous manufacture of a blow molded container and a partially blow-molded, partially compression molded closure within the same blow mold.
Various consumer products, such as food products, are packaged for sale in blow-molded plastic containers sealed with a closure. Typically, the containers are mass produced in high speed blow-molding machines, and the closures, such as caps and lids, are manufactured separately from the containers in injection molds. The separate manufacture of the containers and closures has a significantly impact on the overall cost of mass producing such a package. Such increased costs include manufacturing, tooling and material costs.
Another disadvantage of manufacturing containers and closures utilizing different molding processes is that such processes require the use of different plastic materials which results in the containers being made of one type of plastic material and the closures being made of another. Such a package complicates and increases the cost of recycling the containers and closures and does not readily permit precise color matching between the container and closure. Thus, the separate manufacture of the container and closure also has a negative impact on the aesthetic appearance of the package and its ability to be readily recycled.
To overcome these problems, the assignee of the present application has previously developed and disclosed in International Application No. PCT/US97/03153, published as International Publication Number WO 97/32791 on Sep. 12, 1997, a method for compression molding a closure in the flash material of an extrusion blow mold. To this end, a parison is extruded within a blow mold having a container body cavity and a lid cavity. The parison is blown in the container body cavity to form the container body and is compressed in the lid cavity to form a compression molded lid for the blow molded container. Thus, the lid is formed in the flash material which would otherwise be removed from the container and recycled as scrap material. The entire package can be readily recycled and can be a consistent color throughout.
Other examples of forming articles in the flash material compressed in blow molds include U.S. Pat. No. 4,082,827 issued to Chlystun; U.S. Pat. No. 5,165,558 issued to Cargile; U.S. Pat. No. 3,359,602 issued to Bailey; U.S. Pat. No. 3,369,690 issued to Hayes; U.S. Pat. No. 3,679,785 issued to Dike; U.S. Pat. No. 5,275,780 to Robinson; and U.S. Pat. No. 3,983,199 issued to Uhlig. The Chlystun patent discloses compression molding an integral pull tab; the Cargile patent discloses compression molding a breakaway measuring cup; and the Bailey, Hayes, Dike, Robinson and Uhlig patents disclose compression molding an integral handle.
Other U.S. patents disclose the formation of blown closures within the container body cavity of a blow mold. To this end, the container body and closure are blown as a single intermediate body within a blow mold cavity. The blown intermediate article is then severed and trimmed to form a separate container body and closure. See for instance, U.S. Pat. Nos. 5,553,732 and 5,762,859 issued to Kani; U.S. Pat. Nos. 5,044,923 and 5,213,753 issued to Przytulla; U.S. Pat. No. 3,409,710 issued to Klygisis; and U.S. Pat. No. 5,865,338 issued to Conn. Also see U.S. Pat. No. 5,106,569 issued to Rathman et al.; U.S. Pat. Nos. 4,382,058 and 4,453,911 issued to Watson et al.; and U.S. Pat. Nos. 4,486,164 and 4,486,379 issued to Wilkie et al. for examples of blow molded tool box-shaped containers, or cases, having opposed blow-molded tub-shaped portions integrally connected by a compression molded hinge.
In addition to the need for a cost-effective, readily recyclable and aesthetic container and closure combination and a method and apparatus for making same, there is also a specific need for a substantially tub-shaped container having an upper rim and a novel closure, or lid, for sealing the container. Such a container may be used as a multi-purpose package, for instance, in club or warehouse stores for the sale of powders such as drink powders, candy or any other product capable of being sold in tub-shaped containers. The upper rim of such a container provides a wide opening into the container and is sealed with a relatively large flat lid which spans the opening and engages the rim. Typically, the central most portion of such a lid will warp and otherwise provide an unaesthetic appearance.
Although the above referenced container and closure combinations and methods and apparatus for the manufacture thereof may function satisfactorily for their intended purposes, there is a need for a novel method and apparatus for the cost-effective manufacture of a container and closure combination. In addition, there is also a specific need for a novel container and closure combination which includes a tub-shaped blow molded container and a reinforced lid. The lid should have improved rigidity and definition to prevent warpage and should provide an aesthetically pleasing package. The container and lid should be capable of efficient and simultaneous manufacture in the same blow mold, should be readily recyclable, and should have substantially flawless color matching.
With the foregoing in mind, a primary object of the present invention is to provide a novel method for simultaneously forming a plastic container and associated closure from a single extruded parison in the same blow mold utilizing a combination of blow molding and compression molding techniques.
Another object of the present invention is to a provide a closure, or lid, with increased rigidity and definition so that the lid can be utilized in connection with a wide-mouth tub-shaped container without undergoing warpage and can provide an aesthetically pleasing appearance.
A further object of the present invention is to provide a novel method and apparatus for manufacturing a reinforced closure, or lid, in a blow mold.
A still further object of the present invention is to provide apparatus which enables the formation of various indentations and undercuts to be formed in a blown container and/or closure and which enables ready ejection of the container and a reinforced closure from the mold.
More specifically, the present invention provides a method of manufacturing a plastic container and associated closure in which a parison is extruded within an open set of mold blocks. The mold blocks, when closed, cooperate to form a container forming cavity and a separate closure forming cavity through which the parison extends. The parison located in the container forming cavity is blown to form a container body while a portion of the parison located in the closure forming cavity is separately blown to form at least a part of a closure. A remaining portion of the parison located in the closure forming cavity is compression molded to form a remaining part of the closure which extends integrally from the blow molded part of the closure. Preferably, blow molding of the container body, blow molding of the part of the closure, and compression molding of the remaining part of the closure occur substantially simultaneously. The present invention also provides a container and closure combination made by the above described process.
According to another aspect of the present invention, a novel apparatus for manufacturing a container and associated closure is provided. The apparatus includes a set of mold blocks moveable from an open position to a closed position to capture an extruded parison therein and moveable from the closed position to the open position for releasing a container body and closure therefrom. The mold blocks, when closed, cooperate to provide a blow molded container forming cavity and a separate closure forming cavity which includes a blow-molding section and a compression molding section. A first blow pin is extendable into the container forming cavity for forming a blow-molded container body therein, and a second blow pin is extendable into the blow molding section of the closure forming cavity to blow a portion of the closure. The compression molding section forms a remaining integral compression molded portion of the closure. Preferably, the mold blocks and first and second blow pins are operable to substantially simultaneously form the blow molded container body and partially blow molded, partially compression molded closure.
According to yet another aspect of the present invention, a novel container and reinforced lid combination is provided. The container has an extrusion blow molded body with an upper rim. The lid has a hollow central blow molded portion and a peripheral compression molded portion extending outwardly and integrally from the hollow central blow molded portion. The peripheral compression molded portion of the lid is engageable with the upper rim of the container body to secure the lid to the container, and the hollow central blow molded portion of the lid reinforces the lid structure to increase rigidity and definition and prevent warpage.